In a one-to-many optical communication system applied with a time division multiplex system, in signals in an uplink direction from one or a plurality of slave station apparatuses to a master station apparatus, packets from the slave station apparatuses are burst signals transmitted at intervals. The master station apparatus that receives such burst signals is generally configured from a photo detector (PD) that converts an optical signal into an electric signal, a transimpedance amplifier (TIA) that converts a current signal of a PD output into a voltage signal, a limiting amplifier (LIA) that amplifies a TIA output to amplitude that can be digitally processed, and a clock and data recovery (CDR) circuit that converts an LIA output into a signal synchronizing a system clock.
In a signal detection circuit in a conventional burst-signal reception circuit, to avoid occurrence of a bit error at the head of a burst reception signal due to an AC transient response, the signal detection circuit and the TIA are connected by DC coupling (e.g., Patent Literature 1 described below) or processing for, for example, filling a no-signal section with an idle signal to prevent the AC transient response from occurring even when the signal detection circuit and the TIA are connected by AC coupling (e.g., Non Patent Literature 1 described below).
In Patent Literature 1, a single-phase output of the TIA output circuit is divided into two. One output is directly input to the LIA and the other output is input to an average detection circuit. An average voltage for differential signal generation is obtained from the average detection circuit. Before an output voltage of the average detection circuit reaches an approximate average of a differential signal, the differential signal cannot be reproduced in the LIA adapted to a burst mode located at a post stage of the average detection circuit. Therefore, a data loss occurs at the burst signal head.
Therefore, in Patent Literature 1, to solve this problem, the data loss amount at the burst signal head is minimized by switching, according to an external reset signal, a high-speed time constant average detection circuit that operates at high speed but has a weak tolerance against identical code succession and a low-speed time constant average detection circuit that operates at low speed but has a strong tolerance against identical code succession.
In Non Patent Literature 1, to avoid a DC voltage drift in the no-signal section, a signal having speed same as the speed of a reception signal and having a high low-frequency cutoff frequency (e.g., a PRBS (Pseudo Random Binary Sequence) 7 signal) is extrapolated to the no-signal section. Consequently, a DC voltage after the AC coupling is always the same as the DC voltage at the time of burst signal reception. Therefore, a DC voltage drift does not occur even if the AC coupling is performed by a capacitor having a large capacity (e.g., 0.1 microfarad). It is possible to reduce a preamble length at the burst signal head.